<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        const promise1 = new Promise((resolve,reject) => {
            console.log('promise');
            resolve('resolve'); // 立刻 第一个宏任务 pending -> fullfilled
        })
        // promise.then 的返回值还是 promise
        const promise2 = promise1.then(res => {
            console.log(res)
            return new Promise((resolve,reject) => {
                resolve();
                console.log(promise2,'-----')
            })
        })

        
        console.log(promise2,'-------');
        console.log(1,promise1); // 1 Promise(fullfilled)
        console.log(2,promise2) // 2  Promise(pending)
    </script>
</body>
</html>